Cumulative Risk Assessment for Quantitative Response Data

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The Relative Potency Factor approach (RPF) is used to normalize and combine different toxic potencies among a group of chemicals selected for cumulative risk assessment. The RPF method assumes that the slopes of the dose-response functions are all equal; but this method depends on the choice of the index chemical, i.e. different index chemicals will give different predicted mean estimates. This article is part of an approach to explore and develop cumulative risk assessment strategies. As part of this approach this article proposes a procedure for cumulative risk assessment from exposure to multiple chemicals that have a common mechanism of toxicity. We propose two classification algorithms to cluster the chemicals into subclasses such that the chemicals in the same subclass have a common slope. The joint response is estimated by fitting the dose-response model of the mixture under dose addition. The proposed method will give the same predicted mean response regardless of the selection of the index chemical for the chemicals in the same subclass. The proposed method also allows one to estimate the joint response for chemicals having different slopes. An example data set of six hypothetical pesticide chemicals is used to illustrate the proposed procedure. Copyright ) 2003 John Wiley & Sons, Ltd.